Method for ultrasonic tissue excision with tissue selectivity

ABSTRACT

A surgical method utilizes a cutting blade having a thickness along a cutting edge of between about 0.0005 inch and about 0.020 inch and preferably between about 0.001 inch and 0.010 inch. The blade is moved in contact with relatively hardly tissues which are disposed adjacent to softer tissues at a surgical site in a patient. The blade is ultrasonically vibrated during the moving of the blades, whereby the hard tissue is cut with a modicum of damage being inflicted on the soft tissue.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 14/211,586filed Mar. 14, 2014, now U.S. Pat. No. 10,206,704, and claims thebenefit of U.S. Provisional Patent Application No. 61/791,723 filed Mar.15, 2013, the entire disclosure of which is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

This invention relates to a surgical method. More particularly, thisinvention relates to a method for selectively excising tissue during asurgical procedure. This invention also pertains to an ultrasonicsurgical blade utilizable in performing the method.

Over the past 30 years, several ultrasonic tools have been inventedwhich can be used to ablate or cut tissue in surgery. Wuchinich et al.in U.S. Pat. No. 4,223,676 and Idemoto et al in U.S. Pat. No. 5,188,102disclose such devices.

Ultrasonic surgical devices generally fall into two categories. One is ablunt tip hollow probe that vibrates at frequencies between 20 kc and100 kc, with amplitudes up to 300 microns or more. Such devices ablatetissue by either producing cavitation bubbles which implode and disruptcells, tissue compression and relaxation stresses (sometimes called thejackhammer effect) or by other forces such as microstreaming of bubblesin the tissue matrix. The effect is that the tissue becomes liquefiedand separated. It then becomes emulsified with the irrigant solution.The resulting emulsion is then aspirated from the site. Bulk excision oftissue is possible by applying the energy around and under unwantedtumors to separate it from the surrounding structure. The surgeon canthen lift the tissue out using common tools such as forceps.

A second kind of ultrasonic device uses a sharp blade instead of a blunthollow probe. Here a cutting action takes place. Such a sharp ultrasonicblade is the subject of U.S. Pat. No. 6,379,371. As disclosed therein,the blade shape is semicircular at the distal portion with two straightsides parallel to the longitudinal axis and extending back to theshoulder that contacts the vibrating probe. Male threads are shown whichmate with the female threaded socket of the probe (or transducer) toallow tight intimate contact of the probe and blade tip shoulder. Whenthe two are torqued together, they form a single resonant body that willvibrate in sympathy with the transducer and generator combination. Thedistal end of the blade will vibrate with an amplitude set by themechanical gain of the probe/tip geometry and the input amplitudeprovided by the transducer generator combination. This motion providedthe cutting action for the tissue in question.

The blade of U.S. Pat. No. 6,379,371 was intended for the cutting orexcising of bone or similarly hard tissue in surgical applications. Intests conducted in vitro and in vivo, it was noted that the blade, whensharp, cut both hard and soft tissue with similar ease. In delicateoperations, such as sinus lift surgery or craniotomies where the goal isto cut an aperture in the front of the skull to expose sinus tissue orbrain but not cut the membrane directly beneath the bony structure, thisis very important. It is also important in spinal and brain surgerywhere bone tissue must be cut with a minimum of damage to underlyingsoft tissues such as the dura mater. It was noted in early in vitrotesting that the blade, as it plunged through the cortex of the bonepunctured the membrane or ripped it. After some experience, competentsurgeons were able to master the technique, but the learning curve wassteep.

A sharp blade such as that of U.S. Pat. No. 6,379,371 has been shown inboth in vitro and in vivo testing to be an effective tool for cuttingbone, cartilage, soft tissues such as vein, arteries and can even beused to cut skin with minimal secondary trauma. In this kind of blade,ablation is not the primary cause but a shearing or cutting actionpredominates.

Both the ablating instrument and the cutting or incising instrument havelimitations when used as surgical tools. The blunt probe is effective inablating or excising soft liquid rich tissues such as fat, liver orspleen, but less effective or even non-effective in dry, hard materialsuch as hard cartilage or bone. The blade type devices are effective inthe hard material but also are not soft tissue sparing so thatcollateral tissue damage is incurred, rendering the blade undesirablearound nerve clusters or other important structures. Because sharpblades tend to cut everything, tissue selectivity is reduced to nil andno differentiation may be made between hard and soft material.

In certain applications, such as sinus cavity lifts and maxialfacialsurgery such as third molar extraction, a tool would be useful whichcould cut the harder bony material with less trauma while sparing thesoft tissues underneath if they were inadvertently touched by thevibrating blade.

OBJECTS OF THE INVENTION

An object of the present invention is to provide a surgical method thatselectively excises tissue.

A more specific object of the present invention is to provide a surgicalmethod for cutting harder bony material while minimizing trauma toadjacent soft tissues.

These and other objects of the invention will be apparent to thoseskilled in the art from the drawings and descriptions hereof. Althougheach object is attained by at least one embodiment of the invention, noembodiment need necessarily meet every object.

SUMMARY OF THE INVENTION

The present invention is directed principally to a surgical method ofusing an ultrasonic surgical blade. The preferred surgical blade has acertain range of a critical dimension that permits it to be used in themethod.

The invention was made only upon the observation that the sharper theblade, i.e., the smaller the minor dimension of a vertical trapezoidformed by the included angle of a blade of width N (see FIG. 1), themore likely that cutting of hard tissues resulted in collateral damage,particularly incisions, in surrounding soft tissue. The minor dimensionor thickness of the blade at the edge can range from the width of thebody of the blade, N, to 0. The degree of sharpness is inverselyproportional to the edge thickness.

Dimensionally, it was discovered that blades with an edge thicknessbetween approximately 0.001″ and approximately 0.010″ inch offered thebest compromise between effective, safe cutting of hard tissue such asbone while being sparing of surrounding soft tissue.

As an added benefit, it was serendipitously noted that the blades with aless sharp configuration held their edge longer, i.e., sustained lessdamage than the sharper blades. It should be noted that the blades didnot incur as much damage to the blade surface as the sharper blades, notthat the blades started out not sharp and got worse as they were used.

Accordingly, an ultrasonic surgical blade used in a method in accordancewith the present invention comprises a generally flat blade having athickness along a cutting edge of between about 0.0005 inch and about0.020 inch. More preferably, the cutting edge has a thickness of betweenabout 0.001 inch and 0.010 inch. Most preferably, the cutting edge has athickness of between about 0.001 inch and 0.003 inch. Generally, theblade has a flat body portion with a body thickness greater than theedge thickness. The blade then includes a beveled or tapered regionextending from the body portion to the edge.

A surgical method in accordance with the present invention comprising(a) providing such an ultrasonic surgical blade, (b) inserting the bladeinto bone tissue without a visual aid to enable visual monitoring of theprogress of the blade, (c) during the inserting of said blade,ultrasonically vibrating said blade, the cut formed by said blade beingtoo narrow to allow visual inspection, and (d) terminating the insertingof the blade upon detecting a tactile change indicating contact withsoft tissue.

The tactile change naturally occurs in part because the soft tissue isnot as resistive to the advance of the ultrasonic instrument. Thevibration characteristics of the instrument change upon the tip'sencountering of soft tissue.

Pursuant to special features of the ultrasonic surgical blade, thecutting edge is disposed in a single plane and has an arcuate sectionand a pair of straight sections continuous with the arcuate section atopposite ends thereof. Also, the blade is provided with a shank havingan axially extending bore for the conveyance of cooling fluid to thecutting edge, the blade body being provided with an axially extendingthrough-slot communicating at one end with the bore.

A surgical method in accordance with the present invention utilizes acutting blade having a thickness along a cutting edge of preferablybetween about 0.0005 inch and about 0.020 inch and more preferablybetween approximately 0.001 inch and approximately 0.010 inch and mostpreferably between about 0.001 inch and 0.003 inch. During theperformance of the surgical method, the blade is moved in contact withrelatively hard tissue that is disposed adjacent to relatively softtissue at a surgical site in a patient. The cutting edge may be moved atany angle relative to a surface of the hard tissue, from 90°(perpendicular) to 0° (parallel). In the latter case, the blade may movegenerally along an interface between the relatively hard tissue and therelatively soft tissue. The blade is ultrasonically vibrated during themoving of the blade, whereby the hard tissue is cut and, in the case ofan interface incision, separated from the soft tissue, with a modicum ofdamage being inflicted on the soft tissue.

Pursuant to another feature of the present invention, the vibrating ofthe blade is initiated prior to a contacting of the surgical site withthe blade and is maintained during an initial contact of the blade withthe tissues at the surgical site and during the moving of the blade. Theblade is moved in a continuous and uninterrupted stroke, for instance,along an interface, the ultrasonic vibrating of the blade beingperformed continuously and uninterruptedly during the stroke. At the endof the cutting stroke, the ultrasonic vibrating of the blade isterminated and the blade is removed from the surgical site. Irrigationfluid may be introduced to the surgical site during the moving of theblade along the interface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view, on an enlarged scale, of anultrasonic surgical blade in accordance with the present invention.

FIG. 2 is a perspective view, also on an enlarged scale, of anultrasonic surgical blade in accordance with the present invention.

FIG. 3 is a perspective view, on a larger scale, of a portion of theblade encircled by line III in FIG. 2.

FIGS. 4A-4C are diagrams showing successive steps in an ultrasonicsurgical procedure in accordance with the present invention.

FIGS. 5A-5C are perspective views of a portion of spine, showingsuccessive steps in a spinal surgical procedure in accordance with thepresent invention.

FIG. 6 is a perspective view of a portion of spinal column, showinganother spinal surgical procedure in accordance with the presentinvention.

FIGS. 7A and 7B are perspective views of a portion of spinal column,showing successive steps in a further spinal surgical procedure inaccordance with the present invention.

FIGS. 8A and 8B are perspective views of a portion of spinal column,showing successive steps in yet another spinal surgical procedure inaccordance with the present invention.

FIG. 9A is an elevational view of a spinal column, showing an initialstep in an additional spinal surgical procedure in accordance with thepresent invention.

FIGS. 9B-9D are transverse cross-sectional views of the spinal column ofFIG. 9A, showing additional steps in the surgical procedure of FIG. 9A.

FIG. 10 is a perspective view of a portion of spinal column, showing yeta further spinal surgical procedure in accordance with the presentinvention.

FIG. 11 is a perspective view inside a person's mouth, showing use of anultrasonic cutting blade (as shown in FIG. 2) to cut the lingual ramus.

FIG. 12 is a diagram of multiple mouth and jaw bones showing cuts madeusing an ultrasonic bone cutting blade like that of FIG. 2.

FIG. 13 is a perspective view inside a person's mouth, showing use of anultrasonic bone cutting blade to cut along an oblique line shown in FIG.12.

FIG. 14 is a perspective view inside a person's mouth, showing use of anultrasonic bone cutting blade to cut the tuberosity and the anteriorsinus wall.

FIG. 15 is a perspective view inside a person's mouth, showing use of anultrasonic bone cutting blade to cut the nasal wall.

FIG. 16 is a diagram depicting a lateral osteotomy performed by use ofan ultrasonic bone cutting blade as shown in FIG. 2.

FIG. 17 is a diagram depicting a medial osteotomy performed by use of anultrasonic bone cutting blade as shown in FIG. 2.

FIG. 18 is a diagram depicting a septal osteotomy performed by use of anultrasonic bone cutting blade as shown in FIG. 2.

DETAILED DESCRIPTION

As illustrated in the drawings, a cutting blade 12 for use inultrasonically assisted surgery includes an integral shank portion 14having an external screw thread (not shown) for replaceably mounting theblade to a probe. Alternatively, blade 12 may be permanently attached tothe probe.

Blade 12 includes a planar blade body 16 having a thickness N. Bladebody 16 is provided at an end opposite shank 14 with a blade or cuttingedge 18 including a central circularly arcuate section 20 and a pair oflinear end sections 22 and 24. Edge 18 is continuous along a full radiusof arcuate section 20, as well as along straight sections 22 and 24.

As further illustrated in the drawings, blade 12 also incorporatesstructure providing a path for coolant from an irrigation pump (notshown) to reach blade edge 18, as well as tissues being cut during asurgical procedure. For conducting irrigant to blade edge 18 and thesurgical site, shank portion 14 is formed with an axial passageway orbore 26, which communicates with an axial passageway or bore in theprobe.

Passageway or bore 26 terminates in an open longitudinal channel or slot28 that enables the coolant to spread out and onto the planar body 16 ofblade 12. This open channel or slot 28 distributes irrigant all alongthe sides or lateral surfaces of planar blade body 16 and not in onlyspecific locations, as discussed in U.S. Pat. No. 6,379,371, thedisclosure of which is hereby incorporated by reference. At an end ofchannel or slot 28 opposite passageway or bore 26 is disposed a pair ofopposed inclined surfaces 30 (only one shown) which distribute irrigantfrom the channel or slot towards arcuate blade edge section 20. Thefluid traveling down channel or slot 28 will encounter inclined surfaces30 which exhibit an incident angle that deflects the fluid into the cut(FIG. 10) while minimizing splash back. Surfaces 30 may be planar,convex or concave.

Blade 12 has a thickness E along cutting edge 18 of between about 0.0005inch and about 0.020 inch, more preferably between about 0.001 inch and0.010 inch, and most preferably between about 0.001 inch and 0.003 inch.Beveled or tapered surfaces 32 extend from the body portion 16 to edge18. Cutting edge 18, including sections 20, 22 and 24, is disposed, asis the entire blade body 16, in a single plane.

The use of blade 12 in a surgical procedure is described in detailhereinafter. The procedure described herein is a modification of theprocedure described in U.S. Pat. No. 6,379,371.

In use, blade 12 was found to perform best when the following method wasemployed.

After the patient is prepped for surgery as per standard practices, theultrasound unit is set up as indicated in U.S. Pat. No. 6,379,371. Uponan activation of the ultrasound unit, blade 12 begins to vibrate andirrigation fluid is introduced simultaneously. Blade edge 18 is thenbrought into contact with hard tissue at a preselected surgical site.The vibrating blade 12 is moved in a continuous stroke over the incisionsite to cut or remove tissue to a desired depth. After termination ofthe stroke, the power to the ultrasound unit is shut off and blade 12 isremoved from the surgical site.

The technique discussed above prevents tissue temperature rise to levelsthat would cause necrosis. If blade 12 is not moved across the surgicalsite in a wiping or swiping fashion, tissue temperatures quicklyincrease to over 49 degrees C., which in the human body is at or abovethe necrosis temperature. By constantly moving the blade, thetemperatures rise very little over that of normal body temperatures.Also, this technique provides very good tactile feedback to allow thesurgeon to discriminate between the harder tissue and the softer, viablestructures.

If surgeon desires and there is enough access, he or she may move blade12 so that it cuts along an interface between harder and softer tissues,thereby stripping the harder top layer off the soft tissue underneath.Blade 12 has good selectivity between the two layers, so that collateraldamage to the soft tissue is minimized.

Preferably, a mixture of saline, lidocaine (or equivalent) andepinephrine (or equivalent) is used as the irrigant. Such a mixtureprovides moisturization, a slight hemostasis due to the vasoconstrictingaction of the epinephrine, and pain relief from the action of thelidocaine. All of these chemicals have been found to be safe when usedfor the stated purpose in clinical practice.

Although the surgical method described hereinabove has provenefficacious and safe in adult and pediatric maxialfacial surgery,reconstructive plastic surgery of the face and in various dentalprocedures, many other surgical procedures may benefit from thisinvention. Such other surgical procedures include brain and spinal cordsurgery where bone tissue must be displaced to afford access to thetissues of the central nervous system. The present invention facilitatessuch surgery in that the relatively hard bone tissue may be cut with amodicum of damage inflicted on the underlying relatively soft nervetissues and dura mater. Thus, the present invention is of use in surgerywhere an incision is to be made perpendicularly to an outer tissuesurface or parallel to an exterior surface, e.g., along ahard-tissue/soft-tissue interface.

Ultrasonic bone cutting blade 12 with a blunt tip as disclosed herein isnon-abrasive, tissue selective, cuts longitudinally, and can be usedblindly, that is, without visualizing the operative tip of theinstrument and without significantly damaging underlying soft tissue.The blade cuts a narrow path so that visualization around the blade isnot possible. Damage to underlying soft tissues is prevented insofar asthe bluntness of the blade and the softness of the tissue cooperate todiffuse the energy before irreparable damage is done. Tactile feedbackfrom the instrument enables the surgeon to withdraw the blade from thepatient before the energies delivered to the soft tissue can damage thetissue.

Thus, in using the present surgical blade to cut through bone, one cutstowards the nerve—not away from it. Compared to powered devices likeburr and saw, a blunt blade in accordance with the present inventionprovides better control of the cut and thus higher precision. Third, theblunt blade is tissue selective and provides tactile feedback. Onesenses when going through the outer cortical into the cancellous andfinally touching on the inner cortical layer. Conventional burrs andsaws do not do that and cut as aggressively through any bone and softtissue. Moreover, the surgeon can sketch the kerf as with a fountainpen. No other surgical cutting device offers such a straight pathosteotomy. Saws bend and stray, burrs walk sideways, Kerissons leavebite edges, other piezo devices lack in performance to offer a long anddeep osteotomy. All other piezo or ultrasonic bone cutting devices useserrations with teeth or abrasive surfaces. A surgical cutting blade asdescribed herein allows full and blind insertion of the entire bladelength longitudinally into the bone up to 10/20/30 mm into the bone. Theblade base may act like a safety stop for further insertion.

In using the blunt surgical blade of the present invention, one relieson tactile feedback when cutting. One stops ultrasonic cutting whenbreaching the inner cortical and palpates with the non-active tip inorder to feel one's way through. The method may be used in neurosurgicaland orthopaedic spine procedures including laminectomies, laminotomies,laminoplasties, facetectomies, carpectomies, and bone graft harvestingfrom iliac crest.

A bone cutting blade 12 as described herein with reference, for example,to FIG. 2 works more efficiently with downward (axial) pressure ratherthan side-to-side (lateral) movements. A useful strategy for cuttingbicortical bone consists of the following three steps:

-   -   1. Using lateral movement 40 with little axial pressure to score        the outer cortex of bone to be cut (FIG. 4A).    -   2. Using axial pressure and liberal lateral sweeps 42 to cut        through the cancellous mid-portion 44 of the bone (FIG. 4B).    -   3. Use a controlled cyclical forward/backward movement 46 with        short lateral sweeps 48 to penetrate the inner bone cortex (FIG.        4C). This step primarily involves the use of controlled axial        (downward) pressure. Once the surgeon palpates the intended        breach of the inner cortex, he withdraws the blade 12 slightly        as indicated at 49, moves slightly to one side in a short        lateral sweep 48 and repeats the sequence. It is important to        note that one generally cannot visualize the underlying soft        tissues through the thin trough that is created and must rely on        tactile feedback. If unsure of having penetrated the cortex, the        surgeon can momentarily stop the ultrasonic action, palpate the        inner cortex with the blade 12, and then resume cutting.

In carrying out the above-described surgical technique, one should avoidplunging through the inner cortex of bone in an uncontrolled fashion. Aswith any other surgical tool, such plunging may cut the dura and resultin neural injury. One should not linger over the dura. Once the innercortex in penetrated, the bone cutting blade 12 (FIG. 2) is promptlywithdrawn. Also, one should not use the bone cutting blade 12 when durais adherent to the inner bone cortex (e.g. re-do laminotomy,ossification of posterior longitudinal ligament, etc.). In thesesettings, the dura is at risk, since it cannot move away from the blade12 after the latter penetrates the inner cortex. Furthermore, even ifthe bone is cut uneventfully, elevating it en bloc from the underlyingadherent dura is likely to result in dural laceration.

It is recommended that a prospective user of the bone cutting blade 12develop a tactile “feel” for the blade by practicing on a cadaver. It isimportant not only to develop a feel for when the inner cortex ispenetrated, but also to familiarize oneself with the amount of axialpressure that is required to cut through bone efficiently. One shouldpalpate with the blade 12 turned off. If unsure of whether the innerbone cortex has been penetrated, it is advisable to momentarilyterminate blade vibration and “palpate” the residual bone with blade 12.

It is important to plan an operation. Unlike hand instruments or a powerdrill, blade 12 removes bone en bloc. It is, therefore, imperative thatone plans in advance and defines the boundaries of the bone to be cut.Suggested cutting plans are presented hereinafter for various spineprojects.

Blade 12 must be long enough. If the bone to be cut (e.g. a hypertrophicfacet) is thicker than the longest available bone cutting blade, thebone will have to be thinned with a rongeur or drill before it can becut. Bone thickness can be determined from the preoperative imagingstudies.

An operation can be divided into pieces. Although it may appearcounter-intuitive, it is often more efficient to divide a large bonecutting project (e.g., removing a whole lumber lamina) into two or threesmaller pieces. Doing so will improve visualization of the thicker ordeeper portions of the bone to be cut and will facilitate elevation ofcut bone blocks from the underlying ligaments.

Lumbar Laminotomy

In a lumbar laminotomy, a minimum of three cuts are required: (1) asagittal cut 50 along the base of spinous process SP, (2) a sagittal cut51 along the medial rim MR of the facet joint FJ, and (3) a transversecut 52 in the lamina LA to connect the previous two cuts (FIG. 5A).

When the exposure has been obtained through a small skin incision, onewill find it easier to divide this project into two pieces (FIG. 5B).After making the two sagittal cuts 50 and 51, one may make a transversecut 53 lower on the lamina LA to remove a lower half 54 (FIG. 5B) of thelaminotomy block 55 (FIG. 5A). This provides better exposure of an upperhalf 56 of the laminotomy block 55, which sits deeper in the wound. Theupper block half 56 is mobilized and removed after transverse cut 52 ismade, higher on the lamina.

When a hypertrophic facet joint is present, one may arrange the cutsdifferently, with an additional sagittal cut 57, as depicted in FIG. 5C.First, one makes sagittal cut 50 along the base of spinous process SP,then sagittal cut 57 is made—which is at a more medial location thanthat of cut 51 in FIG. 5A. Transverse cut 52 is made in the lamina LA toconnect cuts 50 and 57.

Transverse cut 52 may extend on a side of sagittal cut 57 opposite cut50. One may then remove a laminotomy block portion 58. Finally, sagittalcut 51 is made along the medial aspect MR of the facet joint FJ and aslice or thin laminotomy block portion 59 is removed. Visualization ofligamentum flavum and dura after the first step aids with the deeperbone cutting that is required in the second step.Lumbar Laminectomy

If one intends to remove only the inferior ′h of the lamina LA, this canbe achieved with three cuts: two sagittal cuts 60 and 61 along eitherside of the spinous process SP, followed by an axial cut 62 across thetop of the spinous process (FIG. 6). Of course, it may be easier toremove the spinous process SP with a rongeur prior to making the laminarcuts 60 and 61. If one plans to remove the entire lamina LA, one shouldconsider removing the inferior ′h first. Then remove the superior ′h asa separate block.

Lumbar Facetectomy

A complete lumbar facetectomy may be required with or without anadjacent laminectomy in certain operations, such as transforaminallumbarinterbody fusion. This can be achieved in a rapid and systematic fashionwith three cuts. (1) A transverse cut 71 is made along the parsinterarticularis. (2) A sagittal cut 72 is made along the lateral aspectof the lamina LA (FIG. 7A). These two cuts allow one to disarticulateand remove the inferior articular process IAP. (3) Once the inferiorarticular process IAP is removed, the tip of the superior articularprocess SAP can be amputated with a single cut 73 (FIG. 7B), thusproviding a pedicle-to-pedicle exposure of the neural foramen and disc.

Cervical Laminectomy and Laminoplasty

A multilevel cervical laminectomy can be performed expeditiously withbone cutting blade 12 by making two parallel cuts 81 and 82 on eitherside of multiple laminae L A (FIG. 8). For open-door laminoplasty, oneshould not penetrate the inner bone cortex on the “hinge” side. Thehinge side can be prepared with a drill. Alternatively, one can use bonecutting blade 12 on the hinge side to make two closely-approximatedouter-cortical cuts (not shown) which intersect at their depth (with aV-shaped profile), then remove a sliver (not shown) of outer-corticalbone to allow the hinge to open.

Anterior Cervical Corpectomy

After discectomies have been carried out above and below the level(s) ofinterest, it is recommended that the anterior portion 90 (FIG. 9C) ofthe vertebral body VB be removed first. To achieve this, parallel cuts91 and 92 are made on either side of the vertebral body VB (FIG. 9A),stopping short of the posterior wall and the posterior osteophytes (FIG.9B). The anterior portion 90 of the vertebral body VB delimited by thetwo cut planes 91 and 92 and two disc spaces 93 and 94 can be removedwith a large rongeur (FIG. 9C). The removal of this bone portion 90provides for better exposure and greater control during a subsequent useof bone cutting blade 12 to make parallel cuts 95 and 96 through theposterior wall PW. A dissected portion 97 of the posterior wall PW isthen carefully elevated and removed (FIG. 9D).

Caution must be exercised to avoid plunging with bone cutting blade 12,particularly in a stenotic canal with cord compression. During elevationof the posterior wall PW, one must avoid rocking one end of thedissected bone portion 97 into the spinal canal SC as the other end isbeing elevated. Finally, this technique is not suitable forcircumstances where the dura may be adherent to the posterior wall PW,as in ossification of posterior longitudinal ligament.

Anterolateral Lumbar or Thoracic Copectomy

This is an advanced ultrasonic bone cutting technique that should beattempted only after one has developed competence and confidence withthe use of bone cutting blade 12 in other operations. The technique forremoval of a thoracic or lumbar vertebral body through an anterolateralapproach is dependent on the pathology for which the operation is beingperformed. Often tumors and infections will have softened the bone tothe point that removal of the mid-portion of the vertebral body does notpresent a challenge. If necessary, bone cutting blade 12 can be used incombination with rongeurs and drills to facilitate this step. Thoroughremoval of bone in this step (to get as close as possible to theposterior vertebral body wall) will facilitate the subsequent steps.

The main challenge is removal of the posterior vertebral body wall toexpose and decompress the spinal canal. After the neural foramen andpedicle are partially exposed and the mid-portion of the body isremoved, a cut 92 is made with bone cutting blade 12 at the junction ofthe ipsilateral pedicle IP and vertebral body toward the spinal canalSC. A second cut 94 is made through the cavity in the vertebral bodytoward the contralateral side of the spinal canal. The posterior wall PW is then carefully elevated away from the canal and removed (FIG. 10).

Maxillary and Mandibular Osteotomies

Bone cutting blade 12 (FIG. 2) may be used to perform maxillary andmandibular osteotomies. The standard blade has a straight configuration,20 mm long and 1.0 mm thick. The distal tip has a rounded shape withbevelled surfaces forming blunt forward-cutting edge 20. Central channel28 ensures the proper distribution of room-temperature irrigant to allcutting surfaces 20, 22, 24 to provide cooling and lubrication, evenwhen the blade 12 is fully engaged in bone. Several modifications may bemade to blade 12 to facilitate maxillary and mandibular osteotomies.Blunt serrations along one longitudinal edge 22, 24 allow bonedissection with one lateral side of the blade, while the contralateralside remains smooth for safe maneuvering within the oral cavity. Depthmarkers may be etched into the blade surface exemplarily at 3, 5, 10,and 15 mm to gauge blade insertion. A soft, protective element made outof silicone may be disposed at the junction with the handpiece toprevent burns to lips or mucosa. The blade length may be extended, forinstance, to 30 mm to accommodate anatomical needs in the maxilla andmandible better.

83 patients (40 males and 43 females) who were scheduled to undergoorthognathic surgery were prospectively enrolled in a study. Thepatients' mean age at the time of surgery was 29 years (range 13-65years). Patients with a previous history of orthognathic surgery wereexcluded from the study. The indications for surgery included thepresence of dimorphisms in 71 patients and symptoms of sleep apnea in 12patients. The study included 49 Le Fort I osteotomies, 19 maxillaryexpansions, 5 mandibular expansions, 102 sagittal split osteotomies, and8 genioplasties. In addition, 40 hi-maxillary procedures were performed.A 20 mm bone cutting blade 12 was utilized for all osteotomies inpatients 1-67, and the 30 mm blade version was used in patients 68-83.The bone cutting blade 12 sold by Misonix, Incorporated under thetrademark BoneScalpel™ operates at a nominal, nonmedulated frequency of22.5 kHz, and the amplitude of vibration ranges from 35 to 300 μm. Whileamplitude settings of 1-10 are available, a setting of 7 was well suitedto the range of bone qualities encountered. Room temperature 0.9% salinesolution is delivered through an integrated peristaltic pump that movesfluid through the central hand piece channel to the blade. The irrigantflow rate is adjustable from 15 to 80 ml/min, which corresponds toconsole settings of 20-100%. Irrigation at setting 100% was chosen tocool the bone and clean the surgical site. All of the surgicalprocedures were performed by two senior surgeons while the patients wereunder general anaesthesia with nasal intubation. The third molars hadbeen removed at least 9 months prior to the orthognathic procedure.

A control scan with a 2 mm thickness (GE Brightspeed) was obtained 2days postoperatively. Examination was made of the ideal bilateralseparation between the maxillary tuberosity and the pterygoid plates.The mandible was digitally isolated from the maxilla and skull toobserve the design of the split with OSIRIX Software. The operative timewas evaluated objectively with OPERA Software. Patients were questionedabout the presence or absence of abnormal sensitivity. Outpatientfollow-ups were performed at 15 days, 2 months and up to 3 years aftereach procedure.

Fracture lines were classified and compared with those reported in theliterature. For the bilateral sagittal split osteotomy (BSSO), thesubperiosteal preparations and dissections were performed as usual. Theosteotomy was initiated at 45° on the lingual ramus side. The nonactiverigid blade in combination with the serrated profile allowed one todetermine the geometry and consistency of the osseous surface (FIGS. 11and 12). According to the preoperative scans, the blade tip penetratedon the oblique line deeply into the cortical bone at a 30° angle in thedirection of the nerve canal without fear of harming the alveolar nerve(FIGS. 12 and 13).

The vertical inferior osteotomy was performed to a level below thebasilar region. The split maneuver was easily performed with manualrotation of the osteotomes. For the Le Fort I osteotomies, thesubperiosteal preparations and dissections were performed in the usualfashion through sulcular incisions. The straight ultrasonic blade waspulled around the maxillary tuberosity without visual control. The bladewas inserted deeper than would be possible with a saw, without fear ofcausing hemorrhage, to weaken the pterygomaxillary junction and theposterior sinus wall (FIG. 14). The blade was then brought back to theanterior sinus wall to penetrate the lateral nasal wall over the entirelength of the septum (FIGS. 15-18). An Obwegeser chisel was applied toall pterygomaxillary sutures, although the disjunction primarilyoccurred during the use of the ultrasonic device. The maxillarydown-fracture was easily obtained with improved control due to anabsence of bleeding.

All 183 osteotomies in 83 patients in this study were performed with theuse of the BoneScalpel™ ultrasonic osteotome. Its ability to engage bonedeeply while maintaining an efficient cutting speed made the use oftraditional power instruments, such as saws or burrs, unnecessary. Theblade design, with its integrated central channel, was effective inproviding irrigant at room temperature to all cutting surfaces,including those that were deep in the bone. Subjectively, theexperimenters noted clear reductions in swelling and hematoma formation.In addition, the experimenters observed the complete absence of dentallesions, hemorrhage, facial palsy and perforations of the nasal mucosa.Only 2 cases were observed to have hypoesthesia (1.96%) of theintra-alveolar nerve. The patients were older and treated for symptomsof sleep apnea. An unsatisfactory split occurred only once (0.98%)during the first use of the 30 mm blade due to insufficient powertransmission, which was rectified in subsequent cases. This patient hadno disturbance of the nerve. Three patients who underwent sagittal splitosteotomy developed an infection on the sagittal side (2.94%) due topoor dental hygiene but did not suffer any significant consequences.

Control scans performed after 2 days in patients 53-83 showed differentpatterns of lingual splitting according to the Plooij et al.classification (Plooij J M, Naphausen M T P, Maal T J J, Xi T, Rangel FA, Swennnen G, et al. 3D evaluation of the lingual fracture line after abilateral sagittal split osteotomy of the mandible. Int J OralMaxillofac Surg 2009; 38:1244-9) and different patterns ofpterygomaxillary separation according to Robinson and Hendy (Robinson PP, Hendy C W. Pterygoid plate fractures caused by the Le Fort Iosteotomy. Br J Oral Maxillofac Surg 1986; 24: 198-202). The results formandibular splitting were 64.8% using Hunsuck's definition and zero badsplits. For the maxilla, 58.3% showed perfect separation of thepterygomaxillary junction without fracture of the pterygoid plates.

Through the utilization of the ultrasonic bone cutting blade 12, withmodifications as pertinent, the most striking observation from 83patients was a significant reduction in bleeding, which resulted in aclean operative field. Thus, osteotomies of the maxilla, particularlythe posterior, were safe and risk free. The placement of retractors canbe optimized to avoid stretching of the nerves because of the inherentsoft tissue-sparing characteristic of the BoneScalpel™ ultrasonicosteotome. Moreover, this procedure can be performed with four hands.

When performing a BSSO, a preoperative scan precisely displays thelingula and the position of the nerve canal into the ramus.

The straight configuration and the stiffness of the BoneScalpel™ bladeserve to increase the accuracy of the osteotomy. Compared withconventional saws and burrs, the ultrasonic blade shows a minimaltendency to deviate from the intended path or walk on bone surfaces.This allows for the placement of the non-active blade in the correctposition prior to activating the ultrasound and engaging the bone, whichis not possible with the saw. Moreover, the working position isdifferent from the drill or the saw and appears to be more ergonomic, asthe blade does not bend during use.

The primary purpose of the serrations added to the lateral side of theblade was to enable the cutting motion along the ramus to remain forwardrather than sideways and in accordance with the proposed 45° tilt angle.The 45° angle is critical for initiating the fracture itself, as thereis no significant cancellous bone present in this portion of themandible.

A traditional osteotomy is characterized by a steep, increasing anglefrom the lingual towards the oblique position. In contrast, theBoneScalpel™ ultrasonic osteotome 12 allows one to continue seamlesslyfrom the lingual ramus towards the oblique at the same 45° angle.Therefore, the cutting force that is introduced at the posterior ramusis better transmitted into the bone, which improves the quality of thelingual osteotomy.

For the horizontal osteotomy, the blade is angled inward towards thenerve canal. The use of the ultrasonic blade is more accurate than therotary burr or reciprocating saw. The sagittal saw blade is far fromrigid, and its lateral flexibility introduces random movements andstraying of the saw tip, which make it difficult to maintain therequired perpendicular position. Moreover, the risk of slippage with theconventional saw blade is high. In contrast, the new procedure utilizingan ultrasonic osteotome enables the osseous cutting to be more preciseand allows for an improved adaption to the anatomy. The tissue-specificcutting resulting from the use of ultrasound technology enables deeperblade insertion for both horizontal and vertical osteotomies, withoutfear of causing nerve trauma, unlike conventional methods. This isfurther facilitated by the marker lines on the ultrasonic blade. Thepropagation of the ultrasonic wave into the cancellous layer facilitatessplitting. The thickness of the blade allows for an improved osteotomyline, in accordance with the available width of chisels used to performthe splitting.

As a result of these improvements, the vertical osteotomy is safer, asthe position of the nerve is preoperatively ascertained from the imagingscan. With the ultrasonic osteotome, it is possible to slip below thebasilar level to reach at least half its width without the risk ofdamaging the facial nerve. The contralateral vertical osteotomy caneasily be achieved by having the surgeon switch sides. In contrast, thereciprocating saw requires caution to maintain a superficial cut andavoid penetrating too deeply into the basilar level, as the inferioralveolar nerve could be located just medial to the cortex.

The kerf is approximately 1.5 mm, which enables osteotomes and a Cryerelevator to be introduced easily above the basal level. This also allowsfor force uniformity during the split. With this approach, theosteotomies are more accurate and deeper, and the forces required forsplitting are much smaller. This also reduces the risk of bad splitsbecause the osteotomies can be well defined according to the individualpatient's anatomy and pathology, and this may result in the use ofosteotomies in more difficult cases, such as cases of asymmetry, olderpatients requiring reconstruction or patients with apnea.

The most frequent surgical morbidity associated with BSSO is damage tothe inferior alveolar nerve caused by direct mechanical injury,postoperative oedema or compression injury after fixation. Unlike thesaw, the straight blade does not require a large dissection for theplacement of the retractor, and minimal sub-periosteal elevationdecreases this risk. Using the BoneScalpel™ ultrasonic osteotome 12,there was no need to change inserts during use, as the entire procedurewas performed utilizing the straight blade.

For LeFort I osteotomies, the blade can be inserted safely without anyvisual control behind the level of the pterygoid. Closed scissors arecurrently only used to verify the disjunction with the contact finger atthe palate. Adequate pterygoid disjunction was confirmed in the group of30 patients who were given immediate postoperative CT scans.

Osteotomy of the pillars and nasal septum can be performed using the 30mm blade without tearing the nasal mucosa. Using the line markers on the20 mm and 30 mm blades, the experimenters did not risk touching theartery, and can confirm that the osteotomy easily reached the innersinus walls, which significantly facilitated the maxillarydown-fracture. When the down-fracture was initiated, the experimenterswere able to complete the osteotomies safely with the BoneScalpel™,especially in the posterior region (i.e. near the emergence of theartery). By entering deeper into the anterior sinus wall, theyeffectively widened the osteotomy and needed to consider a gap of 1.5 mmfor the cephalometric preparation. Compared with the rotary burr orsagitaal saw, the osteotomy line for bone cutting blade 12 is moreregular. In posterior maxillary impaction, the osteotomy of theposterior wall is safer with ultrasonic cutting blade 12.

Recent improvements in ultrasonic surgery have proved to be importantfor advanced orthognathic osteotomies, and the use of ultrasonicinstruments, with their associated benefits, is no longer limited todental surgery. Ultrasonic bone cutting blade 12 with modifications asdiscussed above allows one to improve the techniques for performingmaxillary and mandibular osteotomies in part because of the improvedcontrol over bone cuts and the knowledge that the blade would spare softtissues. This technique resulted in a higher efficiency in the operatingroom when performing orthognathic osteotomies.

Comparative Advantages

In contrast to bone cutting blade 12 (BoneScalpel™), with a burr onecreates a wide trough of 3 mm. As the bone is thinned out it changescolor and becomes transparent. It's a visual marker to stop and switchto Kerisson. When using the burr one removes bone, stops to flush withirrigation, remove debris and to check visually for soft tissues anddepth.

With a blunt surgical blade as described herein, the trough is only0.5-1 mm thick and one can not see inside of the trough. The surgeondoes not see any bone transparency as the gap is too thin. One usestactile feedback to feel the different bone layers.

A blunt blade provided with serrations allows one to place thenon-active blade in an angle on the mandible. The surgeon feels blindlythat the blade is in the right position before engaging the bone andcutting primarily forward with the blunt edge. There is a similarprocedure with the shaver tip. One can place the non-active hook blindlyunder an overhang, feel its correct position and activate the blade.

The lack of wandering/walking/skiving is very important in order to relyon tactile feedback. The blade/tip is put into place and stays were itis. This allows one to cut on curved surfaces.

With a burr, significant effort is necessary to clinically assure thecorrect position: fluoroscopy with significant, dangerous radiationexposure to the surgeon, repeated intraoperative CT scanning,navigation, robotic guidance (drill). While a blunt surgical blade asdescribed herein can be used with navigation it has the potential toeliminate many of the imaging procedures during surgery.

A blunt surgical blade as described herein allows one to cut towards thenerve. Examples are laminectomy, laminotomy, laminoplasty. One can cutdeeper into the maxillary space without fear of damaging nerves andblood vessels, he does that blindly), any type of undercutting, e.g. forharvesting half-thickness bone grafts from the parietal, undercuttingbone blocks in hyperplasia, undercutting the contralateral facet from anipsilateral entry.

The ability to work blindly and precisely is of tremendous value andallows one to alter/adjust surgical techniques. Deeper entry into thepterygomaxillary space improves the Down fracture. Placement of theserrated edge (in the case that the blunt blade is provided with a bluntedge serration) on the mandible improves the sagittal splittheoretically. Any form of undercutting becomes easier as it is lessworrisome. The hemostatic effect is equally important here as it reducesworries as well.

The smaller kerf is theoretically beneficial for osteogenesis. Inplacing an autologous cranial craft it is important to place the graftedge to edge at least on one side to stimulate bone growth. The smallerthe gap the more contact surface there is.

For cervical laminectomies one leaves two cuts bilaterally of 0.5 mmeach, with the burr 3 mm. This results in a bone loss of 1 mm for ablunt blade as described herein versus 6 mm with a burr. It is notablethat Mectron has a 0.3 mm saw.

A blunt surgical blade as described herein allows certain orthognathicor even spine procedures on an outpatient basis due to the added safety.

The tissue sparing relies on a tissue's elasticity. Tissues with highercollagen content are less elastic. Boundaries or stretching of nervescan reduce elastic behavior. This is very important for the ability towork blindly.

Tissue sparing does not work with abrasive surfaces like shavers. Also,spine surgeons are initially afraid of the serrations.

The blade body of the present invention is designed to be fully insertedinto the bone. Examples are the irrigant film over the entire blade, thesafety stop at blade base, the depth markers on the serrated blade.Non-serrated blades may be provided with visual indicators as well forgauging insertion depth. The irrigation channel represents a definedstart and end point and even its middle length point can be seen ashelpful for gauging depth.

Accordingly, it is to be understood that the drawings and descriptionsherein are proffered by way of example to facilitate comprehension ofthe invention and should not be construed to limit the scope thereof.

What is claimed is:
 1. A surgical method comprising: providing anultrasonic surgical blade having a thickness along a cutting edge ofbetween about 0.0005 inch and about 0.020 inch; using said ultrasonicsurgical blade to make at least a first cut and a second cut in a spinalbone of a patient's spine; and removing, from the patient's spine, abone segment bounded on two sides by said first cut and said second cut,respectively, wherein the using of said ultrasonic surgical blade tomake each of said first cut and said second cut includes: inserting saidultrasonic surgical blade into said spinal bone; during the inserting ofsaid ultrasonic surgical blade, ultrasonically vibrating said ultrasonicsurgical blade, said ultrasonic surgical blade preventing a surgeon fromseeing at least a distal-most portion of said cutting edge during theinserting of said ultrasonic surgical blade, where the distal-mostportion of said cutting edge is located inside the patient; andterminating the inserting of said ultrasonic surgical blade upondetecting via tactile sensation on a part of a surgeon a change inresistance to advance of said ultrasonic surgical blade indicatingcontact with soft tissue.
 2. The method defined in claim 1 wherein saidthickness is an edge thickness, said ultrasonic surgical blade having abody portion with a body thickness greater than said edge thickness,said ultrasonic surgical blade including a beveled or tapered regionextending from said body portion to said edge.
 3. The method defined inclaim 2 wherein said cutting edge is disposed in a single plane and hasan arcuate section.
 4. The method defined in claim 3 wherein saidcutting edge includes a pair of straight sections continuous with saidarcuate section at opposite ends thereof.
 5. The method defined in claim4 wherein said ultrasonic surgical blade is provided with a shank havingan axially extending bore for the conveyance of cooling fluid to saidcutting edge, said body portion being provided with an axially extendingthrough-slot communicating at one end with said bore.
 6. The methoddefined in claim 1 wherein said first cut and said second cut extend atan angle relative to one another, said first cut and said second cutintersecting one another.
 7. The method defined in claim 6, furthercomprising using said ultrasonic surgical blade to make a third cut insaid spinal bone, said third cut intersecting at least one of said firstcut and said second cut, said bone segment being bounded on a third sideby said third cut, the using of said ultrasonic surgical blade to makesaid third cut including the inserting, ultrasonically vibrating, andterminating steps of claim
 1. 8. The method defined in claim 7 whereinsaid bone segment is a first bone segment, further comprising: usingsaid ultrasonic surgical blade to make a fourth cut in said spinal bone,said fourth cut intersecting at least one of said first cut, said secondcut and said third cut; and removing, from the patient's spine, a secondbone segment bounded on two sides by said fourth cut and one of saidfirst cut, said second cut and said third cut, the using of saidultrasonic surgical blade to make said fourth cut including theinserting, ultrasonically vibrating, and terminating steps of claim 1.9. The method defined in claim 1, further comprising, prior to theinserting of said cutting blade, manipulating said cutting blade toscore an outer cortex of said spinal bone, the inserting of said cuttingblade including: applying an axial pressure and a lateral sweeping forceto said cutting blade to cut through a cancellous mid-portion of saidspinal bone; and thereafter imparting to said cutting blade a controlledback-and-forth cyclical axial movement with a plurality of lateralsweeps.
 10. The method defined in claim 9 wherein the imparting to saidcutting blade of a controlled back-and-forth axial movement includes:pressing said cutting blade axially into said spinal bone andterminating the inserting of said cutting blade upon tactilely detectinga change indicating contact with soft tissue; withdrawing said cuttingblade axially; and moving said cutting blade laterally inside a cut madeby the applying of axial pressure and the lateral sweeping force to saidcutting blade.
 11. The method defined in claim 9, further comprisingmomentarily interrupting the ultrasonic vibrating of said cutting blade,palpating an inner cortex of said spinal bone with said cutting blade,and subsequently resuming cutting.
 12. A surgical method comprising:providing a cutting blade having a thickness along a cutting edge ofbetween about 0.0005 inch and about 0.020 inch; using said cutting bladeto make at least a first cut and a second cut in a spinal bone of apatient's spine; and removing, from the patient's spine, a bone segmentbounded on two sides by said first cut and said second cut,respectively, wherein the using of said cutting blade to make each ofsaid first cut and said second cut includes: inserting said cuttingblade into relatively hard tissue of said spinal bone located adjacentto relatively soft tissue, so that said cutting edge cuts through saidhard tissue and leaves said soft tissue substantially intact andundamaged; ultrasonically vibrating said cutting blade during theinserting of said cutting blade; forming the respective cut in thepatient by the inserting and ultrasonic vibrating of said cutting blade,the blade preventing a surgeon from seeing at least a distal-mostportion of said cutting edge during the inserting of said cutting blade,where the distal-most portion of said cutting edge is located inside thepatient; and terminating the inserting of said cutting blade upontactilely detecting a change indicating contact with soft tissue. 13.The method defined in claim 12 wherein the vibrating of said cuttingblade in making each of said first cut and said second cut is initiatedprior to a contacting of said spinal bone with said cutting blade and ismaintained during an initial contact of said cutting blade with saidspinal bone and during the inserting of said blade into said spinalbone.
 14. The method defined in claim 12, further comprising introducingirrigation fluid to said spinal bone during the inserting of saidcutting blade into said spinal bone.
 15. The method defined in claim 12wherein said cutting blade is moved in a continuous and uninterruptedstroke during the inserting of said cutting blade, the ultrasonicvibrating of said cutting blade being performed continuously anduninterruptedly during said stroke.
 16. The method defined in claim 12,further comprising, prior to the inserting of said cutting blade,manipulating said cutting blade to score an outer cortex of said spinalbone, the inserting of said cutting blade including: applying an axialpressure and a lateral sweeping force to said cutting blade to cutthrough a cancellous mid-portion of said spinal bone; and thereafterimparting to said cutting blade a controlled back-and-forth cyclicalaxial movement with a plurality of lateral sweeps.
 17. The methoddefined in claim 16 wherein the imparting to said cutting blade of acontrolled back-and-forth axial movement includes: pressing said cuttingblade axially into said spinal bone and terminating the inserting ofsaid cutting blade upon tactilely detecting a change indicating contactwith soft tissue; withdrawing said cutting blade axially; and movingsaid cutting blade laterally inside a cut made by the applying of axialpressure and the lateral sweeping force to said cutting blade.
 18. Themethod defined in claim 17, further comprising momentarily interruptingthe ultrasonic vibrating of said cutting blade, palpating an innercortex of said spinal bone with said cutting blade, and subsequentlyresuming cutting.
 19. The method defined in claim 12 wherein said firstcut and said second cut extend at an angle relative to one another, saidfirst cut and said second cut intersecting one another.
 20. The methoddefined in claim 19 wherein said bone segment is a first bone segment,further comprising: using said cutting blade to make a fourth cut insaid spinal bone, said fourth cut intersecting at least one of saidfirst cut, said second cut and said third cut; and removing, from thepatient's spine, a second bone segment bounded on two sides by saidfourth cut and one of said first cut, said second cut and said thirdcut, the using of said cutting blade to make said fourth cut includingthe inserting, ultrasonically vibrating, forming and terminating stepsof claim 8.